Patrick A. Stadter

Confluence of navigation, communication, and control in distributed spacecraft systems

This research details the development of technologies and methodologies that enable distributed spacecraft systems by supporting integrated navigation, communication, and control. Operating at the confluence of these critical functions produces capabilities needed to realize the promise of distributed spacecraft systems, including improved performance and robustness relative to monolithic space systems. Navigation supports science data association and data alignment for distributed aperture sensing, multipoint observation, and co-observation of target regions. Communication enables autonomous distributed science data processing and information exchange among space assets. Both navigation and communication provide essential input to control methods for coordinating distributed autonomous assets at the interspacecraft system level and the intraspacecraft affector subsystem level. A technology solution to implement these capabilities, the Crosslink Transceiver, is also described. The Crosslink Transceiver provides navigation and communication capability that can be integrated into a developing autonomous command and control methodology for distributed spacecraft systems. A small satellite implementation of the Crosslink Transceiver design is detailed and its ability to support broad distributed spacecraft mission classes is described.

A Weak-signal GPS Architecture for Lunar Navigation and Communication Systems

As envisioned by a broad series of trade studies, the lunar elements of the NASA Exploration Initiative will require a significant increase in navigation and communication capacity. Exploration combines robotic and human mission elements that should ideally support each other in terms of advancing the ability to discover, operate, and support a sustained human presence in the lunar environment. While a small set of individual sorties may be able to incur the inefficiencies of developing mission-specific navigation and communication capability, or relying on current systems, realizing the fundamental goal a sustained human presence will greatly strain current systems. In conjunction with a small spacecraft-based lunar navigation and communication system solution jointly among JHU/APL, NASA/GSFC, NASA/GRC and JPL, JHU/APL analyzed the incorporation of a Global Positioning System component to an infrastructure of spacecraft designed to provide communication and navigation service to lunar assets. This research is described, included the technology basis for reception of GPS in the lunar environment, the impact on the space, ground, and user segments of a lunar navigation and communication infrastructure, and the benefits and costs of such an architectural implementation. Specific technologies include leveraging JHU/APL weak-signal GPS processing and the use of disciplined ultra-stable oscillators.

Lunar Navigation and Communication System Implementation Concept

The NASA exploration Initiative provides a defining vision for the U.S. space program that will include a series of human and robotic missions to the Moon, thereby enabling ultimate exploration of Mars and other destinations. Exploration combines robotic and human mission elements that should ideally support each other in terms of advancing the ability to discover, operate, and support a sustained human presence in the lunar environment. In support of these missions, NASA has considered the implementation of a system to realize lunar navigation and communication service essential to assets at the moon. This paper describes the results of JHU/APLs efforts within a joint study between JHU/APL and NASA/GSFC, with support from NASA/GRC and JPL that details an implementation of a Lunar Relay System that could represent a floor capability of such an infrastructure by providing basic communication and navigation service to lunar assets. The approach provides a flow from a reasonable, if basic, set of requirements and desired capabilities, and details space system implementation that meets those requirements. This includes a conceptual mission design, space and payload segment, ground segment, and operational performance.

Enabling distributed spacecraft system operations with the crosslink transceiver

This research details the development and performance of the crosslink transceiver, an integrated navigation and communication system that enables distributed spacecraft system operations. The crosslink transceiver is a modular, extensible system that supports science operations among multiple, distributed space assets by implementing the essential functions of navigation, communication and control. Distributed spacecraft systems, also called formation flying systems, extend the capabilities of single-spacecraft missions by providing a platform for complex sensing tasks, including multipoint observation, co-observation, and distributed apertures. To accomplish these tasks, such systems rely on the ability to communicate science and coordination information, to determine relative position, velocity and time for command and control operations, and to operate in a coordinated manner to achieve common mission goals. The utility of the crosslink transceiver to support these operations is established by demonstrating its applicability to near-term science and military missions.

Evolvable navigation and communication infrastructure for lunar exploration

The NASA Exploration Initiative provides a defining vision for the U.S. space program and an implementation of U.S. policy that will include a series of human and robotic missions to the Moon with a goal to thereby enabling ultimate exploration of Mars and other destinations. The success of this initiative will rest on the foundation of the initial lunar missions and the ability to develop the means for a sustained human presence on the moon. These missions can be aided and enabled by a navigation and communication infrastructure that can evolve in capability to support lunar operations and data collection. This paper describes a system concept for evolving a lunar navigation/communication infrastructure (LNCI). The described approach uses small spacecraft that are capable of launch as auxiliary payloads. The mission concept is detailed, including spacecraft design, payload concepts and performance estimates for navigation precision and communications coverage. A complete lunar infrastructure would provide global, persistent high-precision navigation and full communications connectivity among lunar elements and the Earth. Detailed herein is an approach for implementation of a prototype LNCI system that would provide navigation and communication services to near-term RLEP missions (e.g., RLEP2 through RLEP4) and demonstrate the LNCI concept such that sustainment of the capability could be transitioned to NASA operational elements and/or industry. The system consists of four small, cost-effective spacecraft that provide radio frequency (RF)-based navigation and communication services from polar orbits. The system concept is designed to evolve by providing improved navigation accuracy and increased communication coverage and bandwidth as additional spacecraft supplement the infrastructure

A scalable small-spacecraft navigation and communication infrastructure for lunar operations

The NASA Exploration Initiative provides a defining vision for the U.S. space program that include a series of human and robotic missions to the Moon, thereby enabling ultimate exploration of Mars and other destinations. The success of this initiative will rest on the foundation of the initial lunar missions. These missions can be aided and enabled by a navigation and communication infrastructure that can evolve in capability to support lunar operations and data collection. This paper describes a system concept for evolving a lunar navigation/communication infrastructure. The described approach uses small spacecraft that are capable of launch as auxiliary payloads. The mission concept is detailed, including spacecraft design, payload concepts and performance estimates for navigation precision and communications coverage. A complete lunar infrastructure would provide global, persistent high-precision navigation and full communications connectivity among lunar elements and the Earth. Detailed herein is an essential first step towards a complete lunar infrastructure that provides continuous navigation and communication support to envisioned near-term lunar missions. The system consists of three small, cost-effective spacecraft that provide radio frequency (RF)-based navigation and communication services from polar orbits. The system concept is designed to evolve by providing improved navigation accuracy and increased communication coverage and bandwidth as additional spacecraft supplement the infrastructure.